1. Field of the Invention
The invention relates to a cage that is suitable for use in, for example, a rolling bearing used to support a main shaft of a wind power generator, and relates also to a rolling bearing including the cage.
2. Description of Related Art
A tapered roller bearing is an example of a rolling bearing that is used to support a main shaft of a wind power generator, and a pin-type cage may be used as a cage of the tapered roller bearing (see, for example, Japanese Patent Application Publication No. 2008-256168 (JP 2008-256168 A)). The pin-type cage includes a pair of cage rings arranged on respective axial sides of tapered rollers, and a plurality of pins arranged at intervals in the circumferential direction and coupled at their respective ends to the cage rings. By passing the pins through through-holes formed along the central axes of the tapered rollers, the intervals between the tapered rollers in the circumferential direction are maintained.
A rolling bearing used to support a main shaft of a wind power generator has a large diameter of approximately 1 to 2 m, and is very large and heavy. Therefore, in recent years, a synthetic resin cage, which contributes to weight reduction of a rolling bearing, has been utilized instead of a pin-type cage. However, the larger a synthetic resin cage is, the more difficult it is to form the entirety of the cage as a single-piece member. Therefore, a split cage formed of a plurality of split pieces arranged in the circumferential direction is usually used (see, for example, Japanese Patent Application Publication No. 2012-77882 (JP 2012-77882 A)).
When the above-described pin-type cage is used, the sliding surfaces of the pins and the sliding surfaces of the tapered rollers, which define the through-holes, require grease lubrication. However, grease does not easily reach the inner part of each though-hole, and therefore the work for supplying the grease is very cumbersome. In addition, it is difficult to handle a large-sized pin-type cage, for example, it is difficult to store and transport the large-sized pin-type cage. On the other hand, it is not so difficult to lubricate and handle a synthetic resin split cage. However, it is somewhat difficult to assemble a rolling bearing including the synthetic resin split cage. That is, in order to assemble the rolling bearing, tapered rollers are fitted into pockets of the cage with split pieces of the cage arranged in a circular manner on the radially outer side of an inner ring. However, because the cage is formed of the split pieces, the pieces of the cage are easily removed from the outer periphery of the inner ring, and, at the same time, the tapered rollers are also easily removed from the inner ring. In addition, it is not possible to enhance commonality of split cage components among rolling bearings having different outside diameters, and it is also difficult to enhance commonality of pin-type cage components other than pins. Therefore, it is difficult to achieve cost reduction through commonality of components among rolling bearings having different outside diameters.